ACE Weekly 12/18/2013 - 12/24/2013 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 12/23/2013 DOY 357 2013 Thrusters 2R 4R+ 4R- Duration 6:10 min Start 13:41:01z Stop 13:47:11z HGAStart -9.05 deg HGAStop +9.00 deg SunStart 14.76 deg SunStop 16.62 deg SpinStart 4.9774 rpm SpinStop 4.9786 rpm Nutation 0.07 deg Firing 31 pulses FuelUsed 0.1031 lbm FuelRemain 109.8504 lbm FinalSCMass 1344.111 lbm The next attitude maneuver is scheduled for Tuesday 12/31/2013. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 349-356 2013 Friday 12/20/2013 - DSN declared the DSS-54 antenna "red" due to excessive noise from one of the azimuth drive points. DSS-54 is tentatively scheduled to return to service on Friday 12/27/2013. Monday 12/23/2013 - DSN decommissioned the DSS-27 antenna. ACE acquired WS1 time for Thursday 12/26/2013 and Friday 12/27/2013 to help relieve contention at DSN. However, WS1 time is less available as the new moon approaches (1/1/2014) and LRO's view overlaps with ACE. ======================================================================== Anomalies: DOY 358 12/24/2013 S-ACE-0672 G13-0015 ITOS event & other problems After the transition to mmocops1p on 12/15/2013 (DOY 349), ITOS had occasional problems (errors from unix directives, not saving Wind attitude data, not forwarding Wind real-time data, command graph errors). The computer was rebooted on 12/24/2013. After the reboot, the ITOS event log was not being saved in the postgres database. The ITOS software was restarted and no problems have appeared since. IMPACT: The operations software (ITOS,MUS,etc) can occasionally be troublesome. Several problems have automatic recovery. Restarting the software and/or the computer can reduce the number of issues. The ITOS event log (cmd times, etc) for the first pass on DOY 358 was lost. Update for S13-0001 Tank Temperature & Spin Rate Anomaly The B1 Fuel Tank temperature increased on 9/19/2013 (18.4C to 19.5C) and 11/05/2013 (to 20.9C). The temperature has continued to rise (to 21.5C) with the rest of the spacecraft as we approach perihelion. At 2053z 12/22/2013, the thermostat for the fuel tank heaters turned off. Background Information - Propulsion Heaters There are 7 propulsion system thermostats that range from 18 to 27C. The following table provides the current used by each set of heaters and the typical state before 12/22/2013. Current Description State before 12/22/2013 ------- -------------------------------- ------------------------------ 0.11A Top Deck Axial Thruster heaters never on 0.11A Top Deck Radial Thruster heaters never on 0.11A Btm Deck Axial Thruster heaters on ~30minutes every 2-3 hrs 0.22A Btm Deck Radial Thruster heaters on ~30minutes every 2-3 hrs 0.23A Internal Lines heaters occasionally on 30 minutes 0.08A External Lines heaters occasionally off 30 minutes 0.38A Tank heaters always on (Internal line heaters rarely turn on during perihelion and turn on ~4 times/day during aphelion.) Since Monday 12/23/2013, the tank heaters have been turning off every 2 hours for ~30 minutes. This has caused the remainder of the propulsion system thermostats/heaters (except for the top deck thruster heaters) to turn on/off to compensate for the changes in temperature. All of the thermostats are functioning as expected, but several propulsion system temperatures are fluctuating by ~5C as the system is not reaching a steady state temperature. This does not seem to be affecting any other spacecraft temperatures (e.g. the instrument deck).